JPH0650905B2 - Video signal switching system - Google Patents

Description

The present invention relates to a video signal switching system in a mobile relay of a television.

In a program (for example, a marathon relay program) that broadcasts a television signal from a television camera installed in a mobile broadcasting vehicle as it is, the television signal is sent to the station by microwave, but in reality, the transmitted microwave is In many cases, it is difficult to always broadcast a good image because it is disturbed by an obstacle. For this reason, a method has been adopted in which the number of receiving points for receiving microwaves from a relay vehicle is increased to one instead of one, and a human selects and transmits an image without any disturbance from among them, but this method is also used. For example, in the case of marathon relay broadcasting in urban areas, there are many obstacles such as pedestrian bridges and road display boards, and obstacles of other vehicles and mistakes in transmission / reception also add to the quality of the received image frequently changing. I will end up. In such a case, it is often not possible to deal with it by manual switching, and the distorted image is often broadcast as it is.

Therefore, an object of the present invention is to provide a video signal switching system in a mobile relay system which enables stable image broadcasting as compared with the conventional art by automatically selecting an image without disturbance.

According to the present invention, a first switch that selects two signals from a plurality of reception points arranged along a relay path, and a synchronous converter that receives two signals selected by the first switch This synchronous converter comprises a (frame synchronizer), and a means for converting the two inputs into digital signals and writing them in the memory, a means for reading the memory at a reference timing, and two digital signals read from the memory. A second switching device to be selected, a converter for converting a digital signal selected by the second switching device into an analog signal, and a second switching device for detecting a disturbance of an image of two inputs to the synchronous conversion device. A video signal switching system in a mobile relay system including a detection circuit for generating the switching control signal is obtained.

In the present invention, only the first selector for selecting the two inputs of the frame synchronizer is manually controlled according to the movement of the mobile relay vehicle to avoid the image disturbance frequently caused by obstacles such as pedestrian bridges and road display boards. Since the switching is automatically performed within the frame synchronizer, there is no timing error, the burden on the switching man is reduced, and stable video can always be output. Furthermore, signal disturbance is detected on the write side of the frame synchronizer, and normal image selection is switched on the read side of the frame synchronizer, so the signal disturbed by using the delay time between the input and output of the frame synchronizer. The normal video selection can be switched before is output.

Next, the present invention will be described in detail with reference to the drawings showing an embodiment of the present invention. FIG. 1 shows an example of switching in a marathon relay, in which the first to fifth microwave receivers 1 have an appropriate interval between the start point S and the turning point M at the start.
5 to 5 are installed, the mobile vehicle 6 transmits to the microwave receivers at the two recent places at different frequencies. In the case of FIG. 1, the first microwave receiver 1 is transmitted at frequency μ ₁ and the second microwave receiver ₂ is transmitted at frequency μ ₂ . In addition, the inside of () in a figure represents the kind of microwave frequency. The reception outputs of the first to fifth microwave receivers are sent to the base station 7.

FIG. 2 is a detailed view showing a scene of the relay in FIG. Assuming that the moving vehicle 6 is at point A in the figure, the electric field strength of the carrier is weakened by the U-shaped pedestrian bridge 8 and reaches the third microwave receiver 3, causing disturbance. On the other hand, the second microwave receiver 2 can receive normally. When the moving vehicle goes a little further and passes point B, the third vehicle
The microwave receiver 3 can receive normally, and the second microwave receiver 2 weakens the electrolytic strength and causes disturbance. In the present invention, switching between the points A and B is automatically performed, and even at the point A
It can be seen that the final output is not disturbed even in terms of points. In addition, when the reception state of the micro changes drastically in such a short distance, there is a limit in predicting switching by a human, and the present invention can prevent the load and mistake of the switcher man from increasing too much. I understand.

Next, the configuration including the frame synchronizer in the base station 7 that receives the signals of the first to fifth microwave receivers 1 to 5 will be described with reference to FIG. The switch 9 is first to
Upon receiving the video signals v _{1 to} v ₅ picked up by the fifth microwave receiver, two signals near the mobile relay vehicle 6 (FIG. 1) are selected and sent to the systems R ₁ and R ₂ .

In the frame synchronizer 10, write addresses corresponding to the respective two inputs are generated and written into the memory. Therefore, the low-pass filter 11, (11 '), A / D converter 12, (12'), write clock generation circuit 13, (13 '), sync separation circuit 14, (1
4 '), frame memory 15, (15'), write address generation circuit 16, (16 '), address selection circuit 17, (1
7 ') are arranged respectively. A read clock generation circuit 18 and a read address generation circuit 19 that generate a read clock from the reference input R ₅ are arranged on the read side.
As a result, the outputs of the frame memories of the systems R ₁ and R ₂ have the same vertical, horizontal, and color phases. The above-mentioned configuration and operation are the same as those of a normal frame synchronizer, and therefore detailed description will be omitted. Frame memory 15, 1
One of the two digital video signals read from 5'is selected by the switching device 20, and is output as a video signal through the D / A converter 21 and the low-pass filter 22.

Next, the control of the switch 20 will be described. Sync signal disturbance detection circuit corresponding to each of the _two input systems R ₁ and R _2.
23 (23 ') and a burst signal disturbance detection circuit 24 (24') are provided to detect the disturbance of the input signal of each input system.
The synchronization signal disturbance detection circuit 23 (23 ') determines whether the synchronization phase is normal or not based on the presence or absence of the synchronization signal and the phase of the previously detected synchronization signal, and outputs a detection signal if abnormal. The burst signal disturbance detection circuit 24 (24 ') detects the level of the burst signal and outputs a detection signal as an abnormality when the level falls below a predetermined level. A switching control circuit 25 for controlling switching of the switch 20 receives four detection signals from the synchronization signal disturbance detection circuits 23 and 23 'and the burst signal disturbance detection circuits 24 and 24', and responds to the logical states of the four signals. The switch 20 is controlled. FIG. 4 is a logic table showing the control of the switching control circuit 25. In this logical table, the priority of the synchronization disturbance is set higher than that of the burst level disturbance, so that the degree of actual failure is well dealt with.

The signals of the systems R ₁ and R ₂ switched according to the theoretical table of FIG. 4 are originally the same signal, and since the color phases are matched by the synchronizer function, only the video level is the same in the two systems. If you leave it, you can switch without any shock, and you can always choose normal or close to it. Furthermore, as described above, all the base stations use the video signal only as a judgment criterion, so no switching information other than the video of the main line is required, and moreover any transmission path between the micro receiver and the switcher (SW1). The main feature is that you can enter. Further, in the present invention, the switching is performed at the digital signal read out from the memory. However, compared with the case where the switching is performed after returning to analog, this is to avoid duplication of the D / A converter and the like, and to reduce the level and phase. It is clear that it is excellent in terms of management.

Although the case of mobile relay has been described as the embodiment of the present invention, it is needless to say that the present invention can be applied to a fixed line or the like where a failure is likely to occur.

[Brief description of drawings]

FIG. 1 is a diagram showing switching in a marathon relay, FIG. 2 is a detailed diagram of a scene in FIG. 1, FIG. 3 is a diagram showing a configuration of an embodiment of the present invention, and FIG. 4 is a diagram in FIG. Logical table of switching control.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Mase 5-3-6 Akasaka, Minato-ku, Tokyo Within Tokyo Broadcasting System (72) Inventor Masashi Onori 5-33-1, Shiba, Minato-ku, Tokyo Japan Within an electric stock company (56) Reference JP-A-58-213569 (JP, A) JP-A-58-75990 (JP, A)

Claims (1)

[Claims] 1. A synchronous converter for synchronizing two video signals with a reference input inputted from the outside, and a switch for selecting one of the two video signals synchronized by the synchronous converter. Disturbance of the sync signal and the burst signal of the video signals of the two systems is detected at the input side of the synchronous converter, and when one system has a disturbance, the other system is selected,
A video signal switching system comprising a switching control circuit for controlling the switching device so as to preferentially select a system having no synchronization signal disturbance when both systems have a disturbance.